Manufacturer's oil change interval recommendations are guesses at best. Whether it is the Jeep owner's manual, the oil manufacturer, or the oil filter company you are using, they just don't know what your conditions are.
So, that leaves us with the age old dilemma of just how often we need to change the oil in our Jeep. Is 3,000 miles too soon? Is 5,000 miles too long? If you change the oil too soon, you are just throwing money away but if you wait too long, and you are destroying your engine
Modern oils feature a slew of additives that help keep varnish, sludge buildup, and other potential issues at bay. At the same time, modern oil features additives that help clean the engine, much like Draino takes care of your toilet.
When the additive package starts to break down, all those things that the oil was designed to combat are no longer being kept at bay. As the additives disappear and the oil starts to break down, and more wear occurs to your engine.
Ideally, you would change your oil right as the last of the additives were used up in the oil. If you could pull your oil out of your engine every day and analyze it and then graph the amount of additives against time or mileage, you'd end up with a Kaufman Curve. Without getting too technical, the Kaufman Curve starts high on the left with a new oil change and gradually decreases, showing the depletion of the additive package. Then as the oil itself breaks down and certain components are broken out of the base oil, the curve can go back up again.
The problem is, oil analysis isn't free, and sending oil out every day is nowhere near practical. Enter the Intellistick; a device that replaces your normal dipstick with a sensor and can send real-time information to either your Windows Mobile Bluetooth enabled device or your Bluetooth enabled computer (if you are within range).
The Intellistick is an electronic system that consists of a smart dipstick and a black processor box. The install is simple, with a ground wire, a constant battery positive, and a mounting location for the box being the only things to figure out. Set the depth of the included sensor-loaded dipstick following the instructions, and you are good to go.
Not only do you get to monitor your oil, but the Intellistick also monitors the oil level (if it goes below about 3/16 of an inch, and alarm is sounded), and the system monitors for water intrusion too (great for if you are crossing streams, rivers, or ponds).
After learning all of that we got our hands on a unit, installed it in our '98 Cherokee, and ran it for 10,000 miles. We are running synthetic in the Jeep, and instead of changing our oil every 5,000 miles, we changed it 7,000 miles after installing the unit. With a decreased oil change interval like that the unit will pay for itself sometime next year. That doesn't even mention the peace of mind from the low oil and intrusion alarms.
In Use
Wherever we went with our Cherokee and ended up popping the hood, people always had questions about the green flashing light (which indicates the system is working correctly). One time we even went so far as to prove the water intrusion sensor worked by pulling the dipstick and plopping it into some guy's water bottle. The red light went off, and our PDA lit up to tell us of the water intrusion.
Unfortunately, what that means is that we didn't accumulate a decent graph to run in this story. By popping the hood and pulling the stick, we ended up with "low oil" and "water intrusion" warnings all over the graph. The device sent info to our PDA just like the company claims it should, and if you want to see or learn more about the Kaufman Curve, check out the Intellistick website.
The other issue we were concerned about was the constant power requirement. We thought that it might draw enough power to drain our battery. We let the XJ sit for a month in the same place, and at the end of the month, after re-priming the fuel system, the Jeep started just like there was no month-long draw off the battery. It cranked strong and proved our constant power worries unfounded.
We tested the unit's claim...
We tested the unit's claim to alert for a low oil situation. Before the dipstick was out of the dipstick tube, the red light on the unit comes on. There is also a corresponding alarm that shows up on whatever device you have installed the software on. The intrusion alarm, such as in the case of water (from a water crossing or a blown head gasket), triggers the same red light on the unit itself with a similar alarm showing up on your screen.
The business end of the stick...
The business end of the stick features an advanced sensor package which feeds information back to the control box. The stick also has graduated hash marks if you are the old-fashioned kind of guy who wants to check the oil level from time to time visually. After our quick low oil test we were confident that the unit would tell us about the oil level, and didn't check it again, even at 7,000 miles.